Horizontal Flip of a frame in Objective-C

I am trying to create a filter for my program (which streams a webcam) which makes the frame flip horizontally, making the webcam act like a mirror.

However, while it compiles and runs, the filter does not seem to have any effect on it.

Here is the code:

CIImage *resultImage = image;
CIFilter *flipFilter = [CIFilter filterWithName:@"CIAffineTransform"];
[flipFilter setValue:resultImage forKey:@"inputTransform"];

NSAffineTransform* flipTransform = [NSAffineTransform transform];
[flipTransform scaleXBy:-1.0 yBy:1.0]; //horizontal flip
[flipFilter setValue:flipTransform forKey:@"inputTransform"];

resultImage = [flipFilter valueForKey:@"outputImage"];

Strangely enough, other filters appear to wo开发者_Go百科rk. For example:

CIFilter * ciEffectFilter = [CIFilter filterWithName:@"CIGloom"];
[ciEffectFilter setDefaults];
CIImage *resultImage = image;
[ciEffectFilter setValue: resultImage forKey:@"inputImage"];
[ciEffectFilter setValue:[NSNumber numberWithFloat: 0.75]
                  forKey:@"inputIntensity"];
[ciEffectFilter setValue:[NSNumber numberWithFloat: 20]
                  forKey:@"inputRadius"];
resultImage = [ciEffectFilter valueForKey:@"outputImage"];


CIFilter *ciCropFilter = [CIFilter filterWithName:@"CICrop"];
[ciCropFilter setDefaults];
[ciCropFilter setValue: resultImage forKey:@"inputImage"];
[ciCropFilter setValue: [CIVector vectorWithX:50 Y:50 Z:300 W:
                         300] forKey:@"inputRectangle"];

resultImage = [ciCropFilter valueForKey:@"outputImage"];

Is it something to do with NSAffineTransform? I have looked around, but I have not found any answers. Thanks heaps!

I'm not sure if this is the problem, but in your first code snippet you are setting two different values for the same key (you set inputTransform twice), I think the first one should be inputImage instead. Try the following instead:

CIImage *resultImage = image;
CIFilter *flipFilter = [CIFilter filterWithName:@"CIAffineTransform"];
[flipFilter setValue:resultImage forKey:@"inputImage"];

NSAffineTransform* flipTransform = [NSAffineTransform transform];
[flipTransform scaleXBy:-1.0 yBy:1.0]; //horizontal flip
[flipFilter setValue:flipTransform forKey:@"inputTransform"];

resultImage = [flipFilter valueForKey:@"outputImage"];

Also, you may need to translate the X axis by the width of the image

[flipTransform translateXBy:... yBy:0];

CIImage *cimage = [[CIImage alloc] initWithImage:image];

You are not Allocating CIImage Object . Try This code.